If one virtual object having depth information is needed to be synthesized with an image, the virtual object may be synthesized with a depth image which has depth information and sense of space or may be synthesized with a two-dimensional image. The two-dimensional image is obtained by capturing a real scene by a camera, so the two-dimensional image has good quality, and the edge, the color, the light pattern and shadow pattern of the two-dimensional image are approximate that of the real scene.
However, because the two-dimensional image does not have any depth information, the virtual object synthesized with the two-dimensional image may have wrong sense of distance or cover an object which should be located at the rear of the virtual object.
Therefore, to make sure the virtual object synthesized with the two-dimensional image have correct light pattern, correct shadow pattern, correct sense of distance and correct positional relationship without affecting the image quality is an important issue nowadays.